An electrochemical system is a system in which a chemical change is accompanied by the passage of an electric current. Electrochemical systems occur in nature or can be man made. An example of a naturally occurring electrochemical system is seen whenever galvanic corrosion occurs, such as when two dissimilar metals are in contact with one another through an electrolyte. A common man-made electrochemical system is a dry or a wet cell battery or a fuel cell. Of the many chemical and physical processes taking place within electrochemical systems, kinetic and diffusion processes are important to characterize since these processes are determinative of the extent to which the electrochemical process proceeds at an acceptable rate. It is desirable to understand the rate-limiting processes taking place in such systems to provide better engineering design or materials of construction to improve the system's performance. Methods have been devised to understand such processes. Electrochemical impedance spectroscopy (EIS) is one tool for analyzing an electrochemical system. In EIS, an alternating electric signal of current or voltage is applied to the electrochemical system. The alternating signal produces a frequency-dependent response of current and voltage from the system. These signals are used to calculate the impedance (Z) of the electrochemical system. In order for EIS to be of any use, the response data collected must be associated with an important aspect of the system under consideration. Analyzing responses from electrochemical systems via EIS is a complex process. Computers provide opportunities for enhancing the analysis by performing faster and more complex algorithms to improve the EIS method. To date, EIS testing equipment uses an approximation by assuming the electrochemical processes, are linear. Using a linear approach, while suitable for some systems, may not be appropriate for others. Furthermore, the linear approach may describe very little of the actual processes taking place within the electrochemical system. Accordingly, improvements are continually being sought to the linear EIS approach.